Technical Field
The present disclosure relates generally to the field of combustion furnaces and methods of use to produce glass, and more specifically to submerged combustion melters and methods for producing foamed glass, hollow or entrained-gas fiber, or non-foamed glass using the submerged combustion melters.
Background Art
A submerged combustion melter (SCM) may be employed to melt glass batch materials to produce molten glass by passing oxygen, oxygen-enriched mixtures, or air along with a liquid, gaseous fuel, or particulate fuel in the glass batch, directly into a molten pool of glass usually through burners submerged in a glass melt pool. The introduction of high flow rates of oxidant and fuel into the molten glass, and the expansion of the gases cause rapid melting of the glass batch and much turbulence, and possibly foaming.
Often it is a primary goal to melt batch or other feed materials in an SCM as quickly and with as small a footprint SCM as possible. Although this is still desired for the most part, one drawback to this strategy in known SCMs is the lack of, or total absence of melter footprint or size outside of the submerged combustion melting zone that might provide some time downstream of the melting zone for treatment of the turbulent, foamy molten glass before it enters downstream equipment. Furthermore, there typically is a lack of, or no melter footprint before the melting zone of an SCM. These failings may severely limit the flexibility of operation of an SCM.
Fining or removal of foam prior to downstream processing may be desired in some instances, while in other instances increased or changed foaming may be desired, for example, when producing hollow fiber or producing products including entrained bubbles. Reduced foaming may be desired in the first case, as the foam may stabilize in a top layer when the molten mass is routed through conventional conditioning and/or distribution channels/systems downstream of the SCM. The foam layer may impede the ability to apply heat to the glass using combustion burners to achieve or maintain temperature and compositional homogeneity of the molten glass, and may also impede the rate at which further bubbles in the melt rise and thus affect expulsion of the bubbles and mass flow rate of the melt in the channels. In extreme cases, the foam generated may interfere with the traditional energy application methods employed, which may cause systems to require shutdown, maintenance and may result in a process upset. Attempts to reduce the foam through process adjustments have not met with complete success in reducing foam to an acceptable amount. On the other hand, in cases where foaming may be desired, control of bubble size, composition, and the like may be hindered in smaller footprint SCMs.
It would be an advance in the glass manufacturing art if submerged combustion melters and processes of their use could address the above restrictions on flexibility of operation.